1. Field of the Art
The present invention relates to a thermoplastic resin composition which comprises a polyolefin, esp., a polypropylene-based polymer containing a specific diene monomer and an olefin polymer rubber, in which the dispersion of the rubber is improved, and which is not only has high strength but also has an excellent balance between moldability, rigidity and impact strength. This invention is concerned also with a method for producing such a resin composition.
2. Related Art
Propylene based polymers have been used as resins useful for general purposes due to their relatively improved moldability, heat resistance and mechanical strength. However, a major problem in their utilization in the form of automotive parts and electric appliance parts is that their rigidity and impact strength at low temperature are inadequate. For possible solution for this problem, the utilization of various fillers or various rubber is being considered. Furthermore, dynamic crosslinking carried out by heat treatment of a particular type of rubber in a dynamic state is now under investigation--see, for instance, JP-A-48(1973)-26838, JP-A-52(1977)-13541, JP-A-53(1978)-81554, JP-A-1(1989)-259074, JP-A-1(1989)-292065, JP-A-2(1990)-60951 and JP-A-2(1990)-73846 specifications.
However, there is still much room left for improvement in the above mentioned propylene polymers with respect to retention of moldability, rigidity and impact strength or maintenance of good balance between them and solvent resistance.